Thank you zdas04 and sailoday28 for the comments. It is greatly appreciated!!!!!!!!
I’m more mechanical than verse in fluids.
In pursuing the same subject, I would like to explain further do-loops I’m going through. In Crane 410 the equations seem to deal mostly with a single pipe and tailor the equations respectively. Especially so, in compressed fluids. With annular flow, the annular cross-sectional area and the equivalent diameter are some what related, which it seems that one will need to be very careful and leery on which equation to use. I have labored through the related compressible equations, and found quite different values when utilizing annulus values and equivalent diameters. I believe, the reason for the differences are directly related with the values of “D” = (Equivalent Diameter derived from a equation with inputs of the two annulus diameters) and “d” = (inside diameter derived from the annulus area equivalent diameter as stated under Hydraulic Radius). With this in mind, it seems that a relevant equation should include the use of “D” and “d”, not “D” or “d”. There is an equation in Crane that seems applicable, Page 3-3 second equation of 3-7. I can solve for P1 because all of the other values are known even though the equations solve directly for mass flow. However if I use the equation just above the second equation, the value for P1 is greatly different when we are looking at 10,000 ft of pipe at high pressures and normal friction factors. The basic difference, in my situation, between the two equations are the inputs of “D” & “A”, and “D” & “d”. When solving for P1, the second equation is anywhere from 40 to 50 % less pressure drop (P1 – P2), than the first equation. By using zdas04’s adjustment, the pressure drop would be less in both equations but still not within let say, 10% of each other equations solution.
My situation has the downstream pressure and CFM required (known) and the upstream pressure and pipe sizing to be supplied and figured out (unknown). In one calculation I need multiple compressors and boosters or larger diameter pipes, and the other equation, one compressor and booster. At $300.00 of diesel a day per machine, the economics are drastic between the equations. The question is, am I on the right track if I utilize the equations with “D” and “d” instead of “D” and “A”? Or am I completely on the wrong track all together? Above variables are in accordance with using Crane’s Nomenclature and Units?
Your comments again are greatly appreciated.
Kris Church
TorqueLock Corp
